<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.10/dist/vue.js"></script>
</head>

<body>
    <div id="app">
        <p>搜索 <input type="text" v-model="goodInfo.search" /></p>
    </div>
    <script>
        Vue.config.productionTip = false;

        const vm = new Vue({
            el: "#app",
            data() {
                return {
                    goodInfo: {
                        search: "oppo",
                        price: 1888,
                        num: 10,
                    }
                }
            },
            watch: {

                /* 
                    1.只监听search的改变(监听对象的某一个属性的写法)
                    "goodInfo.search"() {
                    console.log("重新search");
                    
                */


                goodInfo: {

                    //2.立即监听:初始数据加载后,没有改变的时候就会执行一次回调函数
                    immediate: true,

                    //3.深度监听
                    deep: true,

                    //监听的回调函数,当监听的内容发生改变就会触发

                    //4.watch的回调函数接受两个参数,分别是新值和旧值,但是如果监听的是一个对象,新值和旧值是一样的(除非把对象直接替换了)
                    handler(newVal, oldVal) {
                        console.log("goodInfo中有内容发生改变了", newVal, oldVal);
                    }
                }
            }
        })
    </script>
</body>

</html>